This invention relates to optical recording systems. In particular, this invention relates to modulation and encoding of optical disk media for both reading and writing information in optical recording systems. The modulation and coding system of the present invention provides both clocking and track addressing information.
Known in the prior art, in U.S. Pat. No. 4,238,843 showing a disk-shaped optical record carrier medium having spiral information tracks where a plurality of sectors are divided into a data or information section and a synchronizing section. Each synchronizing section has a prerecorded indicator portion and an address portion. The indicator portion is used to identify the beginning of the sector and also the address portion of the sector. The indicator portion has information recorded thereon so that the signal produced has a frequency domain which is clearly distinguishable from any information component resulting in the address portion or the data portion of the record carrier.
The present invention does not make use of a frequency distinguishable signal for presentation of data information as described in the patent. Instead, the present invention provides a preformatted modulation scheme, using concentric information tracks, for all information including sector, address and data information which may be written using the preformatted clock locations. In addition, the clock locations on the concentric tracks may be varied in a predetermined fashion to be on one side or the other side of the center of the track so that track crossing information can be obtained as a result of detecting different signals resulting from adjacent tracks. This feature is of course primarily susceptible to use in a concentric track record carrier medium, although, the use of concentric information tracks, standing alone, is certainly old in the recording art in general.